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From: Benjamin Riefenstahl <b.riefenstahl@HIDDEN>
To: Eli Zaretskii <eliz@HIDDEN>
Subject: Re: bug#28339: 25.2;
Emacs shows ZWNJ character (Zero Width non-Joiner) as Space
References: <87a81xsc1v.fsf@HIDDEN> <83y3phmca8.fsf@HIDDEN>
Date: Sat, 16 Sep 2017 19:30:05 +0200
In-Reply-To: <83y3phmca8.fsf@HIDDEN> (Eli Zaretskii's message of "Thu, 14 Sep
2017 20:15:59 +0300")
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Hi all,
A few thoughts from an occasional user of this feature.
Eli Zaretskii writes:
> [...] I thought the shaping engine gives us back glyphs that don't
> include ZWNJ itself. Evidently, that's not true, which I find
> strange.
I thought that with OpenType at least that depends on the font? Not
that I trust that fonts do the right thing. I think the right thing for
the font would be to just implement the behaviour (break up ligatgures,
prevent shaping), but not show a glyph. Emacs could of course work
around fonts that *do* show a glyph by rendering the characters before
and after the ZWNJ separately.
For read-only text (Info, Gnus) that is the behaviour that I would like.
For editing, I would like a hair-line type glyph to delete. But I
personally can live with not showing a glyph, and deleting ZWNJ with the
character after it, so that X ZWNJ Y BACKSPACE results in "X". I think
in this scenario multiple ZWNJs should be deleted as one. This is
similar to composed characters, I think.
We should also consider what to do about ZWJ and the bidi directional
control characters. ZWJ handling must come from the font, I think, so
this really can only work when the font works right, but than ZWJ is
probably more rarely used, so it's ok not to try to work around bad
fonts.
Other issues (excuse the verbosity, most of you know all this already,
of course):
* Hightlighting ZWNJ in read-only text while searching for it with
incremental search.
* Read-only parts of buffers that are not completely read-only
(Customize, minibuffer prompts).
* User-specified replacement via display tables.
benny

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From: Nima Aryan <nimawebgard@HIDDEN>
Date: Thu, 14 Sep 2017 21:13:57 +0000
Message-ID: <CALp2H_27GiHg=6DhpUa2Ls4gTui+qgD8CSHBukgb=NRRkEcAOg@HIDDEN>
Subject: Re: bug#28339: 25.2; Emacs shows ZWNJ character (Zero Width
non-Joiner) as Space
To: Eli Zaretskii <eliz@HIDDEN>, handa <handa@HIDDEN>
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--001a114d9354f2908105592cc199
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I've no technical background in typography, but as a use case when the user
type 'A[ZWNJ]B' the editor should show 'A[Discontinuation of continuous
script but without any space or kerning]B'. It can be translated to '[the
end shape of A][No space or kerning][the beginning shape of B]' .
Persian/Hebrew/Arabic scripts have different glyphs for the same character
based on their position in the word (beginning, middle, end), so the ZWNJ
is vital here. Regarding ZWNJ from user point of view in these scripts, it
works exactly like 'Space' but without showing it.
This might be misunderstanding on my part, but It is strange to me if the
font (or shaper?) replaces the ZWNJ with space. It's OK to show nothing for
ZWNJ but not the space. I've not such experience with other editors such as
Gedit (or even with terminal emulators) and if this is the case how other
editors figure it out?
Thanks a lot,
P.s. Regarding the new patch I'll test it as soon as possible.
--001a114d9354f2908105592cc199
Content-Type: text/html; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
<div dir=3D"ltr">I&#39;ve no technical background in typography, but as a u=
se case when the user type &#39;A[ZWNJ]B&#39; the editor should show &#39;A=
[Discontinuation of continuous script but without any space or kerning]B&#3=
9;. It can be translated to &#39;[the end shape of A][No space or kerning][=
the beginning shape of B]&#39; . Persian/Hebrew/Arabic scripts have differe=
nt glyphs for the same character based on their position in the word (begin=
ning, middle, end), so the ZWNJ is vital here. Regarding ZWNJ from user poi=
nt of view in these scripts, it works exactly like &#39;Space&#39; but with=
out showing it.=C2=A0<div><br></div><div>This might be misunderstanding on =
my part, but It is strange to me if the font (or shaper?) replaces the ZWNJ=
with space. It&#39;s OK to show nothing for ZWNJ but not the space. I&#39;=
ve not such experience with other editors such as Gedit (or even with termi=
nal emulators) and if this is the case how other editors figure it out?=C2=
=A0</div><div><br></div><div>Thanks a lot,</div><div><br></div><div>P.s. Re=
garding the new patch I&#39;ll test it as soon as possible.</div><div><br><=
/div></div>
--001a114d9354f2908105592cc199--

Acknowledgement sent
to Nima Aryan <nimawebgard@HIDDEN>:
New bug report received and forwarded. Copy sent to bug-gnu-emacs@HIDDEN.
Full text available.Report forwarded
to bug-gnu-emacs@HIDDEN:bug#28339; Package emacs.
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